Cleaners for conveyors that utilize a scraping element to remove debris and other materials from conveyor belts are well known. These conveyor belts often include metallic splices extending across the belt that run past the scraper blades during conveyor belt operations. The scraper blades are typically biased into engagement with the belt to allow them to resiliently shift away from the belt when surface irregularities on the belt are encountered such as due to the aforementioned metallic splices.
Generally, the goal of keeping the scraper blade in substantially constant contact with the belt to improve cleaning thereof is in competition with the need to allow the blades to shift away from the belt to avoid taking the full brunt of impacts with metallic splices and the like which can cause the scraper blades to rapidly wear. In heavier duty applications, this problem can be exacerbated by the use of thicker, more robust fasteners which create higher impact loads on the cleaning blade.
Another problem for keeping the blade in contact with the belt is its angle of attack relative to the belt. Generally, scalping angles where the blade leans forwardly or in the upstream direction as the belt travels downstream so as to form an obtuse angle with the belt surface upstream therefrom presents the most problems. With this aggressive angling of the blade, it will receive relatively high impact forces when encountering the splices or other carry-back materials on the belt. Also, these high impact forces can cause the blade to vibrate or “chatter” along the belt surface rather than staying in conformance with the belt reducing the cleaning efficiency of the blade. Catastrophic failure of the cleaner blade mounting components utilizing scalping angles is also of greater concern. Similarly, while a cleaning blade extending normal or vertically with respect to the belt surface to be cleaned is more desirable for cleaning, cleaning systems employing blade mounting members that only provide for vertical blade movements still can create high impact forces, particularly on belt splices which can cause excessive wear and ultimate failure of the splices.
By contrast, having the blade extending in the downstream direction so that it forms an acute angle with the belt surface upstream therefrom reduces the impact loading on the blade but can also create difficulties in keeping the blade in conformance with the belt surface. Unless the blade is heavily tensioned into engagement with the belt, when the blade encounters even minor surface irregularities or variations in contour on the belt surface it will undesirably shift too far away from the belt. In other words, the sensitivity of the blade is not optimized in terms of its ability to stay in substantial contact with the belt surface when encountering relatively small irregularities in the surface of the belt that do not cause undue wear of the blade. Accordingly, when these irregularities are due to small pieces of material being carried back on the return run of the belt, the acutely angled blade may not be effective in scraping these off the belt surface. In such instances, it is better for the blade to stay tightly engaged with the belt for wiping the belt clean rather than to resiliently shift away therefrom. Another problem with the acute angle of the blade is that any of the blade mounts extending at the same angle will have the material scraped from the conveyor belt surface falling thereon. If this material build-up increases, it can impair the ability of the scraper blade to effectively clean the belt surface.
For resiliently urging the scraper blades into engagement with the belts, the blade mounts can have pivot biasing mechanisms associated therewith. Generally, these biasing mechanisms have been characterized by their complexity in an effort to enhance cleaning efficiency while reducing blade wear. Particularly, the pivot biasing mechanisms typically employ several pivots and linkages between the conveyor frame and the blade, as well as separate springs such that there are several components which makes these systems more susceptible to wear and failure, see e.g. U.S. Pat. No. 3,952,863 to Schattauer.
Cleaning systems are also known that employ resilient bodies such as of polymeric or elastomeric material as the primary mechanism to resiliently hold the blade in tight engagement with the belt. These types of conveyor systems generally will not be effective in high temperature conditions where the material that is being conveyed and/or the surrounding environment can be at elevated temperatures, such as conveyor belts running at asphalt and cement facilities. In high temperatures, e.g. above 180 degrees Fahrenheit, the polymeric or elastomeric materials can degrade so that the biasing force provided by these bodies dissipates rapidly over time. To this end, material creep for these materials can become a serious problem particularly in high temperature environments where creep can be accelerated. Likewise, the ability of polymeric or elastomeric creep materials undergoing accelerated creep to apply the same bias force to the blade over time will be compromised, as they may lose their ability to return to their original, relaxed configuration with excessive applied stress over long time durations.
Accordingly, there is a need for a conveyor belt cleaner that is better optimized in terms of its cleaning efficiency and the wear resistance of its cleaning blade. Further, a less complex mount for a cleaning blade is needed. A conveyor cleaner system that can be used in high temperature environments would also be desirable.
Another problem with belt cleaning systems employing resilient biasing mechanisms for urging the cleaning blade into scraping engagement with the belt is the impact force with which the blade is returned into engagement with the belt after shifting away therefrom. In many prior systems, it is very difficult to quickly reengage the belt with a cleaning blade that has resiliently shifted away therefrom without returning back into engagement with the belt with an unduly high impact force. The blade impacting against the splice fasteners with high force can damage these fasteners decreasing splice life.
Accordingly, there is a need for a conveyor belt cleaning system that resiliently biases the blade into engagement with the belt and quickly brings the blade back into engagement with the belt while minimizing the return impact force of the blade against the belt and fastener damage caused thereby.